198 ANNUAL REPORT 
Chemical Composition of Standard American Portland Cements. 
———— 
Percentages. 
a 3 ; at gle eee eee Pe eee 
A | Be HO SO | Ba | 4 | as | se 
1 | le) 75 | B68 | GB. | 0.82 mot det.) 1.88 |) 2.62 
2 | 21.20 | 7.90 [not det.) 63.14 | 2.40 |not det.! 1.37 | 2.68 
3 21.93) | 5.98 2.35 | 62.92 | 1.10 |not det.| 1.54 | 3.67 
4 23.36 | 8.07 4.83 | 58.93 | 1.00 0.50 0.85 | 2.90 
5 | 22.89 | 8.00| 2.44 | 63.38 | 2.30 |not det.|not det.| 2.86 
6 222A i226 | 2.54 | 64.96 MaPXS lwo; lei.) Oo4l | BWL 
7 22.04 | 6.45 | 3.41 | 60.92 Be) lao Clay.) BBD | B42 
8 IM ee |) OW oD Aa | B22 ©. 2 0.68 Welk Wy Ao gl 
) | 20.88 10 GS | GB.80 | 2.88 frat dat,| 11S | 2... 
10 MoM) || SOL | Bo 2Zil | 61.62 2.84 not det.) 1.69 | 2.45 
Ngee | 78 | 7a | 220 | cael | TOL bot dea] 2 1 | 2.00 
For comparison, four well-known German Cements are given: 
11 LORSo melo 4380) | O8o09 | sooo not det.inot det.; 2.76 
Wy | Sik 4s | GO. BO 2.50 | 66.04 | 1.11 jnot det. jnot det.| 3.30 
13 Za KO) | BO) 2.28 | 62.28 1.08 inot det.|not det.| 3.10 
14 24.90 | 8.00 3.22 | 59.38 | 0.38 not det./not det. | 3.11 
No. 11, Dyckerhoff; No. 12, Germania; No. 13, Porta; No. 14, Alsen. 
unity is based on the fact that the fundamental formula of clay substance 
is Al,O,, 25i0,, 2H,O, showing one molecule of alumina. This last 
formula therefore tells us that the average clay base corresponds to clay 
of the formula: AI,O,, 0.284Fe,O,, 4.93510,, showing theoretically 
2.93 molecules of free silica under the assumption that none of the alumina 
is part of feldspathic minerals, an assumption which does not hold for 
impure clays. The oxygen ratios between the lime, alumina and silica are: 
3.04: 0.69: 2 making Portland cement equal to a sub-silicate of calcium. 
These molecular ratios are not exact owing to the presence of varying 
amounts of coal ash. 
We might hence compare Portland cement with a basic slag 
with which it shows, indeed, In nature, we do 
many similarities. 
